1. Field of the Invention
This invention relates to medical devices used with, for example, syringes and intravenous (IV) medication dispenser sets and, in particular, relates to a device for enclosing a needle after it has been used so that the needle will not accidentally stick the user.
2. Background Discussion
Many medications are administered by injecting the medication through a needle that has penetrated the body of the patient. The needle is usually removeably attached to a medication dispenser such as an IV set or syringe. When the needle is attached to a syringe, the nurse manually activates a plunger which forces the medication from the syringe through the needle, out the tip of the needle, into the body of the patient. It is common practice to use disposable needles. After the needle has been used, the nurse detaches the needle from the syringe and disgards it. In many instances the nurse will clip the needle, rendering it unsuitable for subsequent use.
The needles commonly employed are contained within a sheath made, for example, of plastic. This sheath grips the needle in a fashion that allows the nurse, while holding the sheath, to attach the needle to the delivery end of the syringe. Ordinarily a Luer lock, or other type of conventional threaded device, is employed which allows the nurse to simply screw the needle onto the delivery end of the syringe. With the needle attached to the syringe, the nurse removes the sheath, exposing the needle. After the needle has been used to inject medication into the patient, the nurse frequently will replace the sheath covering the needle. Ribs on the inside of the sheath engages splines on the barrel hub of the needle upon rotation. The nurse then rotates the sheath and to detach the needle from the syringe. All too frequently in the act of resheathing the needle, the nurse accidentally sticks herself. If the patient is carrying a highly infectious disease, the nurse could be infected. Consequently, a blood test must be conducted on the nurse to see if she is already carrying the disease. This is necessary because if she is not infected at the time of the stick, her employer, the hospital, will be liable.
Accidental needle sticks have been recognized as a serious health hazard and are discussed in U.S. patent application Ser. No. 06/606,679, filed May 3, 1984, entitled Medical Connector, assigned to the same assignee as this patent application. This medical connector employs a needle housed within a cap member so that the nurse is protected against accidental needle sticks. This connector, however, is not suitable for directly administering medication to the patient through a needle which is inserted into the body of the patient. Others have suggested that a protective sheath for the needle be attached to the syringe and movable to cover the needle when the needle is not in use and then retracted to expose the needle. Such devices are illustrated in U.S. Pat. Nos. 4,425,120 and 2,571,653, and 3,134,380, and 2,925,083. These devices, however, all contemplate repeated use of the needle. This would require resterilization after each use and is not consistent with current medical practices which employ disposable needles.